In the extrusion of profile shapes by forcing metal billets through an extrusion die, the profile shapes are typically subjected to conditioning operations and other mechanical operations such as straightening and shearing to a specified length immediately following extrusion. A known extrusion operation begins when a heated billet is placed into the extrusion press and force is applied to one end of the billet, extruding it through an appropriate die. After a small amount of the billet is extruded through the die to form a profile shape, the profile shape is gripped by a suitable gripper mechanism. After sufficient gripping is achieved, the ram of the extrusion press continues to force the metal billet through the extrusion die as an extrusion puller grips the profile shape and applies a pulling force in the direction of the extrusion axis. When substantially all of the billet has been extruded, the ram of the press ceases its forward movement toward the die. Likewise, the gripper ceases its application of pulling force on the profile shapes. At this point, a shear within the press passes across the rear face of the die to shear the butt portion of the billet from the portion of the billet remaining in the die. Thereafter, a new billet is loaded into the press and the extrusion puller and ram may once again apply force to the profile shape to either remove it from the die or continue the extrusion operation.
An important limitation in this process is the requirement that the extrusion puller stop the progress of the profile shape from the extrusion press to the cooling and other conditioning operations while the new billet is loaded into the press and force from the ram is reapplied to the profile shape. This waiting time reduces the overall efficiency of the extrusion operation. It would be more efficient to minimize the time in which the progress of the profile shape from the press to the further conditioning operations is stopped and to speed the return movement of the extrusion puller to prepare for the next extrusion operation.
The U.S. Pat. to Gentry, et al., No. 4,790,167 (issued Dec. 13, 1988) and the U.S. Pat. to Anderson, No. 3,157,268 (issued Nov. 17, 1964) both disclose extrusion handling equipment for conditioning extrusions upon removal of the profile shape from the press. It is known to incorporate such conditioning and handling equipment in the extrusion apparatus to provide for efficient movement of the extrusions away from the extrusion pulling apparatus. Such extrusion handling equipment may include various conditioning means such as a quench tank or spray of cooling medium for quenching the hot extruded profiles. However, uniform properties throughout the profile shapes are not achieved when the progress of the puller and the profile shape must be stopped to load the next billet to allow the profile shape to be separated from the extrusion press. For example, if the quenching means incorporated are spray nozzles directed on the profile shapes immediately after exiting the extrusion die, a portion of the profile shape will be subjected to an excessive amount of quenching medium while the extrusion puller stops to wait for loading of the next billet and reapplication of force from the ram. Likewise, if the quenching medium is a quench tank, the temperature differential between the first extruded end of the profile shape and the last extruded end of the profile shape will be much greater if the progress of the profile shapes toward the quench tank is halted while the next billet is loaded into the billet cavity. These temperature differentials will result in undesirable unequal properties throughout the length of the profile shape.
It is well known to incorporate a single puller head in the extrusion apparatus. Examples of such single puller head extrusion apparatus are disclosed in the U.S. Pat. No. 4,628,719 to Best (Dec. 16, 1986), U.S. Pat. No. 4,307,597 to Elhaus, et al., (Dec. 29, 1981), U.S. Pat. No. 3,881,339 to Mannell (May 6, 1975), and U.S. Pat. No. 3,230,753 to Walker (Jan. 25, 1966).